Men with recent myocardial infarction (MI) or angina, known to be at high risk for sudden coronary death, are identified from a population of about 150,000 men aged 35 to 74 enrolled in the Health Insurance Plan of Greater New York (HIP). They are invited to special examination sessions at which information of importance in developing prognostic data is collected according to a standard protocol. At these examinations, and at several subsequent sessions, the men are monitored with a single ECG lead recorded on a tape cassette. These ECG tapes are processed with a computer methodology whose specificity and sensitivity for classifying abnormal beats as VPBs is checked by systematic physician readings in accordance with a standard protocol. The monitored men are followed for mortality, and information on the circumstances of death obtained from next of kin shortly after the event permits assignment of cause of death. The analysis will include multivariate approaches directed at estimating the contribution to risk of sudden coronary death made by ventricular ectopic activity.